1. Field of Invention
The present invention relates to a variable valve lift apparatus. More particularly, the present invention relates to a variable valve lift apparatus which may vary valve lift according to engine operation condition with simple scheme.
2. Description of Related Art
Generally, an automotive engine includes a combustion chamber in which fuel burns to generate power. The combustion chamber is provided with an intake valve for supplying a gas mixture containing the fuel and an exhaust valve for expelling the burned gas. These intake and exhaust valves open and close the combustion chamber by a valve lift apparatus connected to a crankshaft.
A conventional valve lift apparatus has a fixed valve lift amount using a cam formed in a predetermined shape. Therefore, it is impossible to adjust the amount of a gas that is being introduced or exhausted. Therefore, the engine does not run at its optimum state for various driving ranges.
For example, if a valve lift apparatus is designed to optimally respond to a low driving speed, the valve open time and amount are not sufficient for a high speed driving state. On the contrary, when the valve lift apparatus is designed to optimally respond to a high speed driving state, an opposite phenomenon occurs in the low speed driving state.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.